Why did CP and KCS merge?

Could you possibly shed some light on the reasons behind the merger of CP and KCS? I'm quite curious as to what prompted this union and how it's expected to benefit both parties involved. Is it a strategic move to enhance their market position? Or perhaps a way to diversify their offerings and expand their customer base? Could you elaborate on the potential synergies and opportunities that this merger might bring? I'm also interested in knowing about any challenges that might arise from this integration and how they plan to tackle them. Your insights would be greatly appreciated.